The product of the invention relates to scorch inhibitors added to the polyol during or after its manufacture. Also the scorch inhibitor may be added during the production of polyurethane foams. It is a known problem in the art that existing scorch inhibitors based on conventional amine/phenolic blends cause foam to yellow following exposure to light or NOx fumes. In general, yellowing has been attributed to a variety of sources. For example, reaction products from additives like BHT lead to color bodies such as quinones (K. C. Smeltz, Textile Chemist an Colorist, April 1983, Vol. 15, NO 4), and the polyurethane itself forms color bodies such as diquinone imide as a result of photooxidation (Muller, Plastic Additives, 2nd edition, pg 119). Yellowing also comes from amine substances that presumably oxidize and form color bodies (Muller). It is believed that yellowing may be attributed to amine discoloration.
U.S. Pat. No. 4,058,493 to Pokai et al teaches a foam composition, in which an inhibitor is added. Such additive may be a phenol substituted with tertiary-butyl groups, such as 2,6-di-tert-butyl-4-methylphenol (Ionol(copyright)[BHT]); (or) tert-butyl-catechol; (or) phenothiazine; among others. While such additives may act to inhibit scorch, they may also contribute to foam yellowing when exposed to NOx fumes, ultraviolet radiation or fluorescent light. Importantly, when Ionol (BHT) is used, alone or in blends, excessive yellowing is observed under these conditions, which is undesirable in many consumer applications (e.g. mattress foam).
Therefore, it is the object of the invention to provide an additive to polyurethane foams which inhibits scorch, but which also only minimally contributes to discoloration arising from NOx, ultraviolet radiation and fluorescent light exposure.
The inventors have surprisingly found that an additive based on a combination of a derivatized phenolic, 4-tertbutyl catechol (TBC) and, optionally, phenothiazine (PTZ), is effective against discoloration based on the above factors.
A wide of range of phenolics have been found to be effective, in place of BHT, in combination with the above components. Essentially, it has been found that by substituting at the 4 position of a di-tert-butyl phenolic with a moiety other than methyl (as in BHT), an improved result is obtained. In particular, a 2,6-tert-butyl phenol, substituted at the 4 position with an aromatic, aliphatic or aromatic-aliphatic moiety of C2 or greater, optionally possessing combinations of heteroatoms, preferably N, O, S or P. Optionally, those phenolics possessing combinations of heteroatoms may be dimerized. It is also expected that a 2,4-tert-butyl phenol substituted at the 4 position would also show beneficial effects.
Among these are solid phenolics, such as Anox(copyright) 70 (2,2xe2x80x2-thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]) (formula I), Lowinox(copyright) TBM6 (4,4xe2x80x2-thio-bis-(2-t-butyl-5-methyl-phenol) and Lowinox(copyright) MD24 (1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl) hydrazine) (formula III); all from Great Lakes Chemical Corporation. It is also found that Lowinox(copyright) AH25 (2,5-di-t-amyl-hydroquinone) (formula II) offers improved results. 
More preferred are liquid phenolics, such as Isonox(copyright) 132, Isonox(copyright) 232, both available from Schenectady Chemicals, Inc. and Irganox(copyright) 1135 (Benzenepropanoic acid, 3,5-bis (1,1-dimethyl-ethyl)-4-hydroxy-.C7-C9 branched alkyl estersxe2x80x94CAS Number: 125643-61-0) available from Ciba Specialty Chemicals.
Irganox(copyright) 1135 is benzenepropanoic acid, 3,5-bis (1,1-dimethyl-ethyl)-4-hydroxy-.C7-C9 branched alkly esters (Formula IV): 
Particularly preferred is Isonox(copyright) 232 (2,6 di-tert-butyl-4-nonyl phenol) (Formula V) 
Most preferred is Isonox(copyright) 132 (2,6 di-tert-butyl-4-isobutyl phenol) (Formula VI) 
Thus, the invention resides in a composition to be added to a polyol, during or after the manufacture thereof. Also, the composition may be added during the manufacture of polyurethane foams. Such polyols and foams are manufactured according to well-known methods, such as those set forth in U.S. Pat. No. 5,219,892 to Suhoza.
The basic formulation of the foam used during the testing phase is as follows. Other known foam formulations can be used as well:
The scorch inhibitor (xe2x80x9cAdditivexe2x80x9d in Table I) is a three-component system comprising:
(1) A derivatized phenol, from about 45-95 weight %, preferably 65-75 weight %, more preferably about 66.5%
(2) 4-tert-butyl catechol, from about 5-55 weight %, preferably 22-35 weight %, more preferably about 33%, and
(3) PTZ from 0 to 2 weight %, preferably 0 to 0.75%, more preferably about 0.5% Note: All weights % are weight % based on the total weight of the three-component system.
The scorch inhibitor may be present in the foam formulation based on a range of about 0.25 to 0.75 parts per 100 parts polyol, preferably about 0.30 to 0.60, and more preferably about 0.35 to 0.50.